The term “steganography” generally means data hiding. One form of data hiding is digital watermarking (or simply “watermarking” as used in this document). Digital watermarking is a process for modifying media content to embed a machine-readable (or machine-detectable) signal or code into the media content. For the purposes of this document, the data may be modified such that the embedded code or signal is imperceptible or nearly imperceptible to a user, yet may be detected through an automated detection process. Unlike overt symbologies (e.g., barcodes), an unaided human eye or ear generally will not be able to discern the presence of the digital watermark in imagery (including video) or audio. Most commonly, digital watermarking is applied to media content such as images, audio signals, and video signals.
Digital watermarking systems may include two primary components: an embedding component that embeds a watermark in media content, and a reading component that detects and reads an embedded watermark. The embedding component (or “embedder” or “encoder”) may embed a watermark by transforming (or altering or modifying) data samples representing the media content in the spatial, temporal or some other domain (e.g., Fourier, Discrete Cosine or Wavelet transform domains). The reading component (or “reader” or “decoder”) analyzes target content to detect whether a watermark is present. In applications where the watermark encodes information (e.g., a message or payload), the reader may extract this information from a detected watermark.
A watermark embedding process may convert a message, signal or payload into a watermark signal. The embedding process then combines the watermark signal with host media content and possibly other signals (e.g., an orientation pattern or synchronization signal) to create watermarked media content. The process of combining the watermark signal with the media content may be a linear or non-linear function. The watermark signal may be applied by modulating or altering signal samples in a spatial, temporal or some other transform domain.
The above mentioned orientation pattern is helpful in identifying the watermark signal during detection. It can also provide helpful orientation clues regarding rotation, scale and translation (e.g., distance from origin) of the watermark signal.
A watermark encoder may analyze and selectively transform media content to give it attributes that correspond to the desired message symbol or symbols to be encoded. There are many signal attributes that may encode a message symbol, such as a positive or negative polarity of signal samples or a set of samples, a given parity (odd or even), a given difference value or polarity of the difference between signal samples (e.g., a difference between selected spatial intensity values or transform coefficients), a given distance value between watermarks, a given phase or phase offset between different watermark components, a modulation of the phase of the host signal, a modulation of frequency coefficients of the host signal, a given frequency pattern, a given quantizer (e.g., in Quantization Index Modulation), etc.
The present assignee's work in steganography, data hiding and digital watermarking is reflected, e.g., in U.S. Pat. Nos. 6,947,571; 6,912,295; 6,891,959. 6,763,123; 6,718,046; 6,614,914; 6,590,996; 6,408,082; 6,122,403 and 5,862,260, and in published specifications WO 9953428 and WO 0007356 (corresponding to U.S. Pat. Nos. 6,449,377 and 6,345,104). Each of these above patent documents is hereby incorporated by reference herein in its entirety. Of course, a great many other approaches are familiar to those skilled in the art. The artisan is presumed to be familiar with a full range of literature concerning steganography, data hiding and digital watermarking.
One combination described in this disclosure is a method including: obtaining a first color channel and a second color channel, the first color channel and the second color channel are components of a color image signal or color video signal; obtaining a digital watermark orientation pattern, the orientation pattern serving to facilitate detection of a watermark message; separating the digital watermark orientation pattern into first frequency components and second frequency components; utilizing a processor or electronic processing circuitry, transforming the first color channel by steganographically embedding the first frequency components therein; and utilizing a processor or electronic processing circuitry, transforming the second color channel by steganographically embedding the second frequency components therein.
Another combination described in this disclosure is a method including: obtaining a first color channel, a second color channel and a luminance channel, the first color channel, the second color channel and the luminance channel are each components of a color image signal or color video signal; obtaining a digital watermark orientation pattern, the orientation pattern serving to facilitate detection of a watermark message; separating the digital watermark orientation pattern into first frequency components, second frequency components and third frequency components; utilizing a processor or electronic processing circuitry, transforming the first color channel by steganographically embedding the first frequency components therein; utilizing a processor or electronic processing circuitry, transforming the second color channel by steganographically embedding the second frequency components therein; and utilizing a processor or electronic processing circuitry, transforming the luminance channel by steganographically embedding the third frequency components therein.
Still another combination described in this disclosure is an apparatus including: a processor; and instructions for execution by the processor. The instructions include instructions to: i) obtain a first color channel and a second color channel, the first color channel and the second color channel are components of a color image signal or color video signal; ii) obtain a digital watermark orientation pattern, the orientation pattern serving to facilitate detection of a watermark message; iii) separate the digital watermark orientation pattern into first frequency components and second frequency components; iv) transform the first color channel by steganographically embedding the first frequency components therein; and v) transform the second color channel by steganographically embedding the second frequency components therein.
Yet another combination described in this disclosure is an apparatus including: a processor; and instructions for execution by the processor. The instructions include instructions to: i) obtain a first color channel, a second color channel and a luminance channel, the first color channel, the second color channel and the luminance channel are each components of a color image signal or color video signal; ii) obtain a digital watermark orientation pattern, the orientation pattern serving to facilitate detection of a watermark message; iii) separate the digital watermark orientation pattern into first frequency components, second frequency components and third frequency components; iv) transform the first color channel by steganographically embedding the first frequency components therein; v) transform the second color channel by steganographically embedding the second frequency components therein; and iv) transform the luminance channel by steganographically embedding the third frequency components therein.
In some other combinations described in this disclosure, a watermark message signal (e.g., a payload carry component) may be inserted into one or more color channels along with isolated frequency components of an orientation signal for that channel.
Further combinations, aspects, features and advantages will become even more apparent with reference to the following detailed description and accompanying drawing.